Staffie types can play quite rough and be intimidating to other breeds. It sounds like puppies learning their manners from what you describe though. Id work on a good recall and make sure he has some command to stop playing when you decide he has to stop.
As long as he backs off if the other dog yelps and only growls or barks to defend himself (without pursuing the other dog) then it sounds like he is becoming a polite freindly boy. Also make sure he doesnt develop the habit of dominating other dogs when he's older. My chihuahua gets fairly irritated when staffs stomp on top of him after he's already submitted. They usually get a nip for their trouble..